A pressure control device for use in a control system of an automatic transmission of a motor vehicle has been used in the past. A typical pressure control device is shown in U.S. Pat. No. 4,579,145, issued Apr. 1, 1986, in the name of Leiber et al. This patent discloses a pressure control device including a housing which encases a magnetic coil and an armature. A control slide is actuated by the armature and movable within a valve through which a pressure medium to be controlled passes. A plunger is carried by the armature. A pin loaded with control pressure is arranged at the end of the control slide opposite to that facing the plunger and acts on the control slide.
The problem with the above device is that low magnetic forces are required to move the spool valve, resulting in poor response and potential fouling. Further, the spool valve is dependent upon the position of the solenoid armature. This requires the hydraulic flow forces to enter into the armature force balance and allows parasitic forces to be transmitted by the spool valve to the armature which has a large effect on the regulation of the device. Also, there is poor manufacturability because of the need to maintain a precise position between the armature, spool valve and its ports.